Professional coffee machine

ABSTRACT

A professional coffee machine includes a supporting frame; a boiler mounted thereon with a tank of at least 8 liters receiving water and heating it to a temperature of about 122-130° C. for the thermo-controlled production of pressurized steam; a preheater having a first heat exchanger associated to the boiler so that the boiler water heats, by heat exchange, the supply water crossing the first exchanger to a first temperature T 1  that is lowerly close or substantially equal to a second temperature T 2 , optimal for preparing a coffee infusion; a dispensing unit of the coffee infusion having its own thermo-controlled heating element, configured to bring the water outlet from the preheater to the second temperature T 2 , if T 1  is less than T 2 ; a thermal insulating member that mechanically constrains the dispensing unit to the supporting frame; and a dispenser of pressurized steam in communication with the tank.

The present invention relates to a professional coffee machine.

Coffee machines are known, which are intended to be used in coffee shopsfor the production of increased quantities of coffee, tea and similarinfusions, cappuccinos and other hot beverages.

A coffee machine for professional use is to be capable of meetingincreased stresses due to intense use. In particular, a professionalcoffee machine, intended for example to be used in a coffee shop, is tobe capable of preparing a few hundred, and even thousand, coffees everyday, and of processing even 200 liters of milk a day, and this forseveral years.

Any professional coffee machine comprises a frame, to which a boiler ismounted for the production of hot water and pressurized steam generallyat a temperature of 122° C. and a pressure of 1.2 bar.

The boiler is supplied with supply water and is provided with a firstoutlet, which crosses a solenoid valve or manual tap, which is suppliedby a first spout for dispensing hot water for the preparation of tea andother infusions. The boiler is also provided with a second outlet whichcrosses another solenoid valve or another manual tap which is suppliedby a second dispensing spout of a steam flow for heating the milk and/orfoaming.

After a significant quantity of hot water has been taken from the boilerto prepare a tea infusion or a coffee infusion, new cold water entersthe boiler and induces a sudden cooling of the water therein with thesubsequent alteration of the optimal conditions of use of the coffeemachine for the whole time required to restore operating conditions.

Traditional professional coffee machines again are designed for eachcoffee dispensing unit of a heat exchanger accommodated in the boilerand intended to heat the water for the preparation of espresso coffee.It is supplied with supply water which is pressurized by a pump, and issized so as to provide exiting water at 82-85° C., which is introducedinto the dispensing unit fastened to the machine frame and provided withquick coupling and uncoupling means of a traditional filter holder.

If the features of a professional coffee machine are well known and theoperating method thereof is just as known, what diversifies one coffeemachine from another is its performance. It is associated with specificconditions of use, which in turn subject the coffee machine tosignificant stresses in the use thereof, and it is associated with theneeds resulting from the uses and different habits from one country tothe next.

For example, according to the types of coffee, these require a differentgrinding particle size and this affects also the temperature andpressure values of the infusion water, which in turn affect the flavor,color and aroma of the coffee infusion. And since coffee is the basicingredient for a series of different beverages (espresso coffee, coffeewith milk, cappuccino, etc.), it is easy to understand that thepreparation of a coffee with constant and repeatable organolepticfeatures for any type of blend is not a problem which is easily solved.

Another problem with traditional professional coffee machines is theneed to generate superheated steam in such quantities so as to be ableto heat large quantities of milk, as requested in certain countries(U.S.A., Germany, Australia). This results in the quantity of cold waterwhich enters the boiler for restoring that released as pressurized steamfor heating the milk, cooling the water in the boiler and indirectly thehot water which is released from the exchanger for the preparation ofthe coffee infusion, with the drawbacks indicated above.

Moreover, known professional coffee machines are to also meet the needsencountered in the different countries and which often are contrastingin nature. If indeed the preparation of increased daily quantities ofmilk is required, there is a need to have high pressure steam available,while if a little milk is to be frothed, there is a need to make lowpressure and low flow steam available.

Another problem with known professional coffee machines is that the hotwater to be used for the preparation of the tea infusion and the like isthe same boiler water which generates the pressurized steam for heatingand frothing the milk. However, when the water is released from thedispenser, it has a greater pressure and higher temperature than theambient ones and it is not suitable for preparing tea and otherinfusions.

Another problem with known professional coffee machines and associatedwith needs of contrasting nature consists in the need on the one hand tohave a large thermal inertia of the machine in order to absorb thetemperature variations of the water associated with the continuousdispensing of hot water and with its restoration with cold water, and onthe other hand the need to have a low thermal inertia to obtain a promptresponse of the machine to the temperature adjustment system.

WO 2011/145064 describes a machine for household use which is notsuitable for increased productions of coffee, tea or milk. Inparticular, since it is not a professional machine, it has and dealswith completely different needs.

In greater detail, the machine of WO 2011/145064 comprises a tank forthe water which is sent, by means of a pump, to a first heater where itis heated to generate hot water to be used for the preparation of thecoffee infusion. Furthermore, the water already heated by the firstexchanger, or directly the tank water not heated, is sent to a secondheater for generating steam to be sent to a corresponding dispensingspout.

In particular, the second heater does not comprise a tank in which thewater is balanced with the steam, and this leads to the deduction thatit is configured for the instantaneous generation of low flow steam.However, such a type of steam generation is incompatible withprofessional needs, in which increased productions of steam arerequired, also in particularly close succession.

EP 2133011 instead describes a professional machine, exclusively for thepreparation of coffee. In particular, such a machine comprises a boilerwhich receives the cold supply water, and a circuit in which the coldsupply water is conveniently mixed with the heated water outlet from theboiler so as to cause it to reach a first temperature. Then, the waterat such a first temperature is sent to a dispensing unit which comprisesa heater which is configured to bring the water to a second temperaturecorresponding to the optimal one for dispensing the coffee infusion. Themachine of EP 2133011 does not in any manner provide for the generationof pressurized steam for heating and/or frothing the milk.

It is the object of the invention to provide a professional coffeemachine capable of resolving all the above problems, also contrasting innature, which are encountered in current professional coffee machines.

It is another object of the invention to provide a professional coffeemachine in which maintaining the optimal temperature of the hot waterfor the preparation of the coffee infusion is ensured.

It is another object of the invention to provide a professional coffeemachine capable of quickly responding to the hot water temperatureadjustment system for the preparation of the coffee infusion.

It is another object of the invention to make a professional coffeemachine which simultaneously allows both a fine-tuned and quickadjustment of the temperature of the water to be used for the coffeeinfusion, and the dispensing of pressurized steam for heating/frothingthe milk.

It is another object of the invention to provide a professional coffeemachine in which various pressures and steam flows to the dispensers maybe used without affecting the ability to maintain the optimaltemperature for the preparation of the coffee infusion.

It is another object of the invention to provide a professional coffeemachine capable of generating hot water for the preparation of the teainfusion and the like, at the proper temperature required for thatspecific use, without affecting the ability to maintain the optimaltemperature of the water for the preparation of the coffee infusion.

It is another object of the invention to provide a professional coffeemachine which has an alternative characterization with respect totraditional ones, both in terms of construction and performance.

It is another object of the invention to provide a professional coffeemachine which can be obtained in a simple, quick manner and with lowcosts.

All these objects, both individually and in any combination thereof, andother objects which will become apparent from the description below, areachieved according to the invention by a professional coffee machine asdefined in claim 1.

The present invention is hereinbelow further clarified in a preferredembodiment thereof, which is described by mere way of non-limitingexample, with reference to the accompanying drawings, in which:

FIG. 1 shows a perspective and general view of a professional coffeemachine according to the invention,

FIG. 2 shows the simplified hydraulic diagram thereof,

FIG. 3 shows an exploded perspective view of a dispensing unit and themethods for constraining it to the coffee machine frame,

FIG. 4 shows an exploded perspective view of the pressurized steamdispenser, and

FIG. 5 shows the horizontal section of the pressurized steam dispenser.

As shown in the drawings, the professional coffee machine is similarexternally to traditional coffee machines, i.e. it has a frame 2 towhich all the functional components of the machine are applied, whichare referred to, insofar as useful to the comprehension of the presentinvention, during the course of the description below.

Hereinbelow, “professional coffee machine” means a coffee machineintended to be subjected to intense use, i.e. to be capable of preparinga few hundred, and even thousand, coffees every day, and of processingeven 200 liters of milk a day, and this in a particularly quick manner,without requiring stop times between successive preparations, and forseveral years.

The dispensing units 4 of the coffee infusions, the dispensers 6 ofpressurized steam for heating and frothing the milk and a dispenser 8 ofhot water for the preparation of the tea and other infusions inparticular are fastened to frame 2 of the machine. An outer body 10,which protects and conceals all functional internal machine componentsfrom sight, is applied to frame 2.

A boiler 12 is mounted to frame 2, which boiler comprises a tank 11having a capacity of at least 8 liters and is provided with an inlet 14of the cold supply water and an outlet 16 for pressurized steam.Advantageously, the hot water (liquid component) inside the tank 11 ofboiler 12 is balanced with the superheated steam (gaseous component).

The outlet 16 for pressurized steam puts the upper inner space of thetank 11 of boiler 12, which is occupied by the steam, in communicationwith the steam dispenser 6 through a solenoid valve 18 and a fine flowregulator 20, the details of which are described below.

Boiler 12 is provided with traditional heating means of the watercontained in its tank 11, and these preferably consist of an electricalresistance 22, even though they could consist of other means, e.g. a gasburner or other.

Boiler 12 is also provided with traditional control members, such as inparticular a thermal probe, which detects the temperature of the waterinside its tank 11, and a level sensor 26 of the water itself.

Finally, boiler 12 is fastened to frame 2 of the coffee machine by meansof blocks made of thermal insulating material (not shown), which servethe function of avoiding the formation of heat bridges between theboiler itself and frame 2 and accordingly, between the boiler itself andthe parts of machine fastened to frame 2.

Two heat exchangers 28 and 30 are associated with boiler 12, which aresupplied at inlet with the cold supply water and are connected at theoutlet to the dispenser 8 of hot water for the preparation of the teaand other infusions, and with the dispensing unit 4 of the coffeeinfusion, respectively. In particular, the water in the tank 11 ofboiler 12 acts as a heat-carrying fluid for the heat exchangers 28 and20. In greater detail, the water which crosses the heat exchangers 28and 30 heats up, thus absorbing the heat which is transferred by thewater in the tank 11 of boiler 12.

Advantageously, as will be more apparent below, exchanger 30 in realityacts as a preheater for the water intended to prepare the coffeeinfusion.

If the coffee machine is provided with several dispensing units 4 of thecoffee infusion, there are provided just as many preheaters 30 in boiler12, even if for simplicity, reference is made in the present descriptionto one dispensing unit 4 alone and to one preheater 30 alone.

In greater detail, the dispensing unit 4 of the coffee infusioncomprises a heater 31 consisting of a metal body 32 preferably havingfeatures both of a low heat transmission coefficient and high specificheat (e.g. OT58), which is constrained to a flat portion of frame 2 ofthe coffee machine by means of two blocks 34 made of thermal insulatingmaterial, preferably of synthetic type having features both of a lowheat transmission coefficient and a high mechanical resistance (e.g.PVDF).

In particular, as depicted in FIG. 3, each block 34 is fastened to frame2 of the coffee machine with screws 36 which cross a metal plate 38 andblock 34 before being engaged in frame 2, and it is also fastened tounit 4 with other screws 40, which cross a different metal plate 42 andblock 34 before being engaged in body 32 of the dispensing unit 4.Advantageously, all direct metal connections between the dispensing unit4 and frame 2 of the machine thereby are eliminated, and therefore therelated heat bridge between the two.

In particular, a conduit is formed in body 32, for the water frompreheater 30 and intended to reach the chamber in which the coffee blendis contained. A traditional filter holder 46 provided with one or moredispensing and outlet spouts 48 of the coffee infusion conveniently isapplied to such a chamber.

An electrical resistance 44 is embedded in the body 32 of heater 31,which resistance allows to heat up the body itself, and therefore alsothe water which flows in the conduit defined in said body and comingfrom preheater 30. A temperature sensor 50 connected to the control unitwhich supplies the electrical resistance 44 and a solenoid valve 52which can be actuated by the operator or by the control unitconveniently is arranged in the conduit inside the body 32 of the heater31 of unit 4.

The hot water dispenser 8 for preparing the tea infusion is connected tothe outlet of exchanger 28 through a solenoid valve 54 or through a tapwhich can be actuated manually by the operator.

As said, the dispenser 6 of pressurized steam is connected to the outlet16 of boiler 12 through the solenoid valve 18 and a flow regulator 20.

In particular, as depicted in FIGS. 4 and 5, this flow regulator 20comprises a body 56 having an inner cylindrical cavity 58 whichcommunicates upstream with the outlet of the solenoid valve 18 anddownstream with the steam dispensing spout 60.

There may be provided a cylindrical rod 62 in cavity 58, provided withan end portion equipped with a worm screw gear 64, which is engaged in agraduated actuation wheel 66, which may rotate with respect to body 56but is prevented from performing axial movements because it is engagedby a fork-shaped element 67 fastened to body 56 itself.

The rotation of rod 62 is prevented by a fork 71 fastened integrallythereto and slidingly constrained to body 56 so as to allow only axialmovements of the rod itself.

Rod 62 has a reduced-section portion 68, which following its axialmovements induced by the rotation of wheel 66, more or less obstructsthe communication between conduit 73 associated with the solenoid valve18 and the conduit 75 defined in spout 60.

A pair of O-rings 70 ensures the seal between cavity 58 and the outsidefor any axial position of rod 62.

The operation of the coffee machine according to the invention is asfollows:

under stand-by condition (i.e during the rest position in which thepreparation is not required of any beverage), the temperature of thewater in the tank 11 of boiler 12 is adjusted to a higher value thanthat of traditional coffee machines (which generally is equal to about122° C.) and practically is from 122° C. to 130° C., and preferably isequal to or greater than about 128° C., and is balanced with the steamin the upper part of tank 11. In particular, as shown in the diagram byMollier, the pressure of the water in the tank 11 of boiler 12 isadjusted to a higher value than that of traditional coffee machines(which generally is equal to about 1.2 bar) and practically is from 1.2bar to 1.8 bar, and preferably is equal to or greater than about 1.6bar.

Advantageously, this allows to ensure an increased production of highpressure and high flow steam, and more particularly allows to obtain acoffee machine which practically can be used in all markets, and inparticular in the markets where the preparation, for example for heatingand/or frothing, of increased daily quantities of milk (over 200 litersof milk a day) is required.

The temperature of the water in the tank 11 of boiler 12 conveniently iscontrolled by a probe, which acts on a control unit (not depicted),which in turn acts on the electrical resistance 22 in a traditionalmanner.

Preheater 30 of the water intended to prepare the coffee infusion issized so that at those temperature conditions of the water of boiler 12,the water intended to then supply the dispensing unit 4 reaches a firsttemperature T₁, for example from 60° C. to 70° C., preferably of about65° C., which is lower than a second temperature T₂ which corresponds tothe optimal one for the preparation of a specific coffee infusion. Inother terms, by crossing the heat exchanger of preheater 30, the coldsupply water is heated up to reaching a first temperature T₁ byabsorbing the heat which is transferred from the water in the tank 11 ofboiler 12 and which acts as a heat-carrying fluid.

Heater 31 of the dispensing unit 4, and in particular resistance 44thereof, is controlled so as to ensure that the water contained thereinreaches said second temperature T₂, i.e. the optimal temperature for thepreparation of the coffee infusion, which generally is from 70° C. to95° C., preferably of about 82-85° C.

Conveniently, the heat exchanger of heater 28 of the water intended toprepare the tea infusion is sized so that at those operating conditionsof boiler 12, the water reaches a third temperature T₃, which issuitable for preparing the tea infusion, i.e. at a temperature of about70° C.-90° C.

Conveniently, if for example the frothing of the milk is required forthe preparation of a cappuccino, or in any case milk requires heating,the operator will actuate the solenoid valve 18 so that the pressurizedsteam in the tank 11 of boiler 12 is released through dispenser 6, thuscreating a steam flow for heating and possibly frothing the milk. If adifferent pressure of the steam is required, the operator may act on thegraduated wheel 66 and thereby adjust the pressure of the steam which isreleased from the dispenser to set it to the value desired, which willthen remain constant each time the solenoid valve 18 is actuated and upto new adjustments by means of the wheel itself.

It is worth noting that even if increased quantities of steam forheating/frothing increased quantities of milk are taken from boiler 12,the quantity of hot water corresponding to these increased quantities ofsteam is rather low and the quantity of cold water which is to beintroduced into the tank 11 of boiler 12 for restoring the waterreleased in the form of steam is equally as low. Advantageously, thisensures maintaining a significantly constant temperature of the waterinside the boiler itself.

If the preparation of a coffee infusion is required, the operatoractuates the solenoid valve 52, which induces the release of waterpushed by a traditional electrical pump (not depicted) towards thecoffee powder at the optimal temperature (which corresponds to thesecond temperature T₂) required by the operator for that specific typeof coffee so as to cause the desired infusion to be released from spout48.

Since the preheater 30 is sized so as to provide the water release at atemperature T₁ which corresponds or is close to the optimal temperatureT₂ for the preparation of the coffee infusion, it is apparent that thesignificantly constant temperature of the water of boiler 12 ensures anincreased constancy in temperature of the water which is released frompreheater 30, and therefore just as increased a constancy in temperatureof the water with which the coffee infusion is prepared.

But even if temperature T₁ of the water which is released from preheater30 undergoes small variations related to small variations of the waterinside boiler 12, the heater 31 provided inside the body 32 of thedispensing unit 4 would quickly take the temperature of the water backto the optimal value T₂ given the low thermal inertia of the unit itselfand the increased sensitivity thereof to the heat regulation system.

If the preparation of a tea infusion is required, the operator actuatesthe solenoid valve 54 to induce the release of water through dispenser 8at the optimal temperature T₃ for this function.

From the above description, the professional coffee machine according tothe present invention is much more advantageous than traditional coffeemachines because:

-   -   due to the use of water which is heated by the boiler water by        means of heat exchangers, its phenomenon of abrupt temperature        lowering is avoided each time new cold water enters the boiler        to replace that which is released in the form of pressurized        steam for heating/frothing the milk;    -   due to a boiler operating under temperature and pressure        conditions which are fixed and no longer bound to the different        parameters required for the preparation of various quantities        and preparation methods of frothed milk, water preheated to a        fixed temperature close to that used for the preparation of the        coffee infusion may be used;    -   due to the heating of the water for the preparation of the        coffee infusion in two steps, with a preheating in the boiler to        take the water to a temperature close to that of use, and with a        final heating in the coffee dispensing unit, and due to the low        thermal inertia thereof, there is a very quick response to the        heat regulation system;    -   due to the particular system for constraining the coffee        dispensing unit 4 to the coffee machine frame, increased heat        insulation features of the unit itself are combined with an        increased resistance to the inevitable mechanical stresses to        which it is subjected during the operations of applying and        removing the filter holder;    -   due to the heating of the water for preparing the tea infusion        by means of exchanger, the machine has hot water available at        the optimal temperature even with a boiler temperature which is        higher than habitual ones, which does not allow the direct use        of the boiler water for the preparation of the tea infusion;    -   due to the fine adjustability of the steam flow, the machine        allows to have thermal energy in sufficient quantity to heat        significant quantities of milk on the one hand, and on the other        hand to use the low pressure steam for frothing limited        quantities of milk, when required.

In particular, the machine according to the invention is different fromWO 2011/145064 in that the latter:

-   -   is not a professional machine, rather is a household machine,    -   does not have a boiler comprising a tank of at least 8 liters        which is connected with the pressurized steam dispenser,    -   does not have, in sequence, a preheater which is associated with        the boiler and is configured to heat the water to a first        temperature T₁, and a heater which is associated with the        dispensing unit of the coffee infusion and is configured to heat        the water from said first temperature T₁ to a second temperature        T₂ which is the optimal one for that specific type of coffee,    -   does not provide for the supply water crossing the preheater to        be heated by the water in the boiler by means of heat exchange,    -   does not provide for the coffee dispensing unit to comprise a        heater and to be constrained to the machine frame by means of        thermal insulating means.

Furthermore, the machine according to the present invention is differentfrom EP 2133011 in that the latter:

-   -   does not provide for the boiler to be sized for the        thermo-controlled generation of pressurized steam and to be        connected with a pressurized steam dispenser,    -   does not have a preheater which is associated with the boiler so        that the water contained in said boiler heats, by heat exchange,        the supply water which crosses the preheater itself;    -   does not provide for the heater of the coffee dispensing unit to        be constrained to the machine frame by means of thermal        insulating means.

Essentially, while the aforesaid traditional professional machinesdirectly use the water in the boiler for the preparation of the coffeeor tea infusion, the professional machine according to the presentinvention uses the water of the heater as a heat-carrying fluid forheating the water to be used for the preparation of the coffee or teainfusion by means of heat exchangers. In other terms, in the presentinvention, the water of the boiler releases heat to the water whichcirculates in the preheater, thus causing the heating of the latter to afirst temperature T₁ which is close (that is, slightly less) or equal toa second temperature T₂, which instead is the optimal one for thepreparation of that specific coffee infusion. This is particularlyadvantageous because it allows a fine-tuned and quick adjustment to beobtained of the temperature of the water to be used for the coffeeinfusion and simultaneously allows dispensing pressurized steam toheat/froth the milk.

The invention claimed is:
 1. A professional coffee machine comprising: asupporting frame (2); a boiler (12) mounted on said supporting frame (2)and comprising a tank (11) of at least 8 liters which is supplied withwater and which is provided with a heating device heating the water to atemperature of about 122° C.-130° C., said boiler being configured for athermo-controlled production of pressurized steam; at least onepreheater (30) for preparation of a coffee infusion, comprising a firstheat exchanger which is associated with said boiler (12) so that thewater contained and heated in said boiler (12) heats, by heat exchange,supply water that crosses said first heat exchanger to a firsttemperature T₁, said first temperature T₁ being in lower proximity orsubstantially equal to a second temperature T₂, which corresponds adesired temperature for the preparation of the coffee infusion; adispensing unit (4) of the coffee infusion provided with athermo-controlled heating element (44), which is configured to bring awater outlet from said preheater (30) to said second temperature T₂, ifsaid first temperature T₁ is less than said second temperature T₂; athermal insulating member (34) for mechanically constraining saiddispensing unit (4) to said frame (2) of the coffee machine; and adispenser (6) of the pressurized steam in communication with the tank(11) of said boiler (12).
 2. The professional coffee machine accordingto claim 1, wherein the water inside the tank (11) of the boiler (12) isbalanced with the pressurized steam.
 3. The professional coffee machineaccording to claim 1, wherein said first heat exchanger of saidpreheater (30) is sized so as to generate hot water at the firsttemperature T₁ comprised between 60° C. and 70° C., when the hot waterin said boiler (12) is at a temperature of 122° C.-130° C.
 4. Theprofessional coffee machine according to claim 1, wherein saidthermo-controlled heating element (44) of said dispensing unit (4) isconfigured to ensure that the water reaches or maintains said secondtemperature T₂, which is comprised between 70° C. and 95° C.
 5. Theprofessional coffee machine according to claim 1, wherein saiddispensing unit (4) is mechanically constrained to said supporting frame(2) through blocks (34) of a synthetic material having a low heattransmission coefficient and a high mechanical resistance, saiddispensing unit (4) and said supporting frame (2) being independentlyconstrained to said blocks (34).
 6. The professional coffee machineaccording to claim 1, wherein said dispenser (6) of the pressurizedsteam is connected with the tank (11) of said boiler (12) with a conduit(16) provided with an intercepting member (18) and an adjusting member(20) of steam flow.
 7. The professional coffee machine according toclaim 1, further comprising, for preparation of a tea infusion, a heatercomprising a second heat exchanger (28) associated with said boiler (12)and configured so that the water contained and heated in said boiler(12) heats, by heat exchange, supply water that crosses said secondexchanger (28) to a third temperature T₃, said third temperature T₃corresponding to a desired temperature for preparation of the teainfusion.
 8. The professional coffee machine according claim 7, whereinsaid second heat exchanger (28) is configured so as to generate hotwater at said third temperature T₃ of approximately 70° C.-90° C. whenthe water in said boiler (12) is at a temperature of 122° C.-130° C. 9.The professional coffee machine according to claim 1, wherein saidboiler (12) is mounted on said supporting frame (2) with a thermalinsulating constraining element.
 10. A professional coffee machinecomprising: a supporting frame (2); a boiler (12) mounted on saidsupporting frame (2) and comprising a tank (11) of at least 8 literswhich is supplied with water and which is provided with a heating deviceheating the water to a temperature of about 122° C.-130° C., said boilerbeing configured for a thermo-controlled production of pressurizedsteam; at least one preheater (30) for preparation of a coffee infusion,comprising a first heat exchanger which is associated with said boiler(12) so that the water contained and heated in said boiler (12) heats,by heat exchange, supply water that crosses said first heat exchanger toa first temperature T₁, said first temperature T₁ being in lowerproximity or substantially equal to a second temperature T₂, whichcorresponds a desired temperature for the preparation of the coffeeinfusion; a dispensing unit (4) of the coffee infusion provided with athermo-controlled heating element (44), which is configured to bring awater outlet from said preheater (30) to said second temperature T₂, ifsaid first temperature T₁ is less than said second temperature T₂; athermal insulating member (34) for mechanically constraining saiddispensing unit (4) to said frame (2) of the coffee machine; and adispenser (6) of the pressurized steam in communication with the tank(11) of said boiler (12), wherein said dispensing unit (4) comprises itsown heat exchanger connected at an input with said preheater (30) and atan output with a filter holder (46) provided with at least onedispensing spout (48) of the coffee infusion.
 11. The professionalcoffee machine according to claim 10, wherein said dispensing unit (4)comprises a metal body (32) made of a material with a low heattransmission coefficient and a high specific heat.
 12. The professionalcoffee machine according to claim 11, wherein a conduit for passage ofthe water coming from said preheater (30) and intended to reach saidfilter holder (46) is obtained in said metal body (32), and anelectrical resistance (44) for heating said water is also obtained insaid metal body (32), said electrical resistance being supplied by acontrol unit controlling a temperature sensor (50) arranged in saidconduit, downstream of said temperature sensor (50) there being provideda solenoid valve (52) which is adapted to be actuated by an operator orby said control unit.
 13. A professional coffee machine comprising: asupporting frame (2); a boiler (12) mounted on said supporting frame (2)and comprising a tank (11) of at least 8 liters which is supplied withwater and which is provided with a heating device heating the water to atemperature of about 122° C.-130° C., said boiler being configured for athermo-controlled production of pressurized steam; at least onepreheater (30) for preparation of a coffee infusion, comprising a firstheat exchanger which is associated with said boiler (12) so that thewater contained and heated in said boiler (12) heats, by heat exchange,supply water that crosses said first heat exchanger to a firsttemperature T₁, said first temperature T₁ being in lower proximity orsubstantially equal to a second temperature T₂, which corresponds adesired temperature for the preparation of the coffee infusion; adispensing unit (4) of the coffee infusion provided with athermo-controlled heating element (44), which is configured to bring awater outlet from said preheater (30) to said second temperature T₂, ifsaid first temperature T₁ is less than said second temperature T₂; athermal insulating member (34) for mechanically constraining saiddispensing unit (4) to said frame (2) of the coffee machine; and adispenser (6) of the pressurized steam in communication with the tank(11) of said boiler (12), wherein said dispenser (6) of the pressurizedsteam is connected with the tank (11) of said boiler (12) with a conduit(16) provided with an intercepting member (18) and an adjusting member(20) of steam flow, and wherein said adjusting member (20) of the steamflow comprises a body (56) having an inner cylindrical cavity (58)communicating upstream with said intercepting member (18) and downstreamwith a spout (60) for dispensing the pressurized steam, a shutter (62)which controls passage of the steam flow with its axial position beingaxially movable in said inner cylindrical cavity.
 14. The professionalcoffee machine according to claim 13, wherein said shutter (62) consistsof a single rod associated, by its axial movements, with a graduatedwheel (66).
 15. The professional coffee machine according to claim 14,wherein said rod (62) is has a cylindrical shape and has areduced-section portion (68) which controls the passage of the steamflow through said body with the axial position of said rod (62).